Home > Articles

Systems Perfomance Advice for Programmers

Koder-with-attitude Kode Vicious provides advice for systems performance including problems with debugging, documenting, and testing the system.

Save 35% off the list price* of the related book or multi-format eBook (EPUB + MOBI + PDF) with discount code ARTICLE.
* See informit.com/terms

This chapter is from the book

This chapter is from the book

The time has come

The Walrus said

To speak of many things

“The Walrus and the Carpenter,” Lewis Carroll

Stepping away from the kode in front of us, we come to a slightly broader set of koding koncepts. Many people fail to understand that programming and software design aren’t just about typing hundreds of lines into an editor or IDE and then pressing Run. There are concepts we must address no matter how large or small the system is that we’re working with. As any system is built there are the problems of debugging, documenting, and testing the system as well as understanding challenges to the overall system performance, and these are some of the problems we turn to in this chapter.

2.1 Ode to the Method

The good thing about science is that it’s true whether or not you believe in it.

Neil deGrasse Tyson

If computer science is truly a science, then clearly the scientific method can be applied to solve problems that present themselves in computers and their accompanying software. A topic rarely covered in computer science programs is how one might actually apply the scientific method to software engineering. If one is not solving a problem via something akin to the scientific method, then can they be said to be debugging by faith? Faith-based debugging has, thankfully, not taken off in the way agile and scrum have, but it is definitely a method I have seen applied by many people who really ought to know better. Treating software bugs as near supernatural occurrences is a frequent joke among koders, “Did you sacrifice a chicken?” being a common retort to someone saying that they simply cannot find a bug or get the printer to work. While there are koders who are so good that they can find the bug just by scanning a page of your kode, these are few and far between, and so the best programmers learn to apply what, in essence, is the scientific method to solving their problems. In the following response I lay out a very simple way to apply the method to fixing software bugs and being confident in the fix.

Dear KV,

I just started working for a new project lead who has an extremely annoying habit. Whenever I fix a bug and check in the fix to our code repo, she asks, ”How do you know this is fixed?” or something like that, questioning every change I make to the system. It’s as if she doesn’t trust me to do my job. I always update our tests when I fix a bug, and that should be enough, don’t you think? What does she want, a formal proof of correctness?

I Know Because I Know

Dear I Know,

Working on software is more than just knowing in your gut that the code is correct. In actuality, no part of working on software should be based on gut feelings, because, after all, software is supposed be a part of computer science, and science demands proof.

One of the problems I have with the current crop of bug-tracking systems (and trust me, this is only one of the problems I have with them) is that they don’t do a good job of tracking the work you’ve done to fix a bug. Most bug trackers have many states a bug can go through: new, open, analyzed, fixed, resolved, closed, etc., but that’s only part of the story of fixing a bug, or doing anything else with a program of any size.

A program is an expression of some sort of system that you, or a team, are implementing by writing it down as code. Because it’s a system, you have to have some way of reasoning about that system. Many people will now leap up and yell, ”Type systems!” and ”Proofs!” and other things about which most working programmers have no idea and which they are not likely ever to come into contact with. There is, however, a simpler way of approaching this problem that does not depend on a fancy or esoteric programming language: use the scientific method.

When you approach a problem, you ought to do it in a way that mirrors the scientific method. You probably have an idea of what the problem is. Write that down as your theory. A theory explains some observable facts about the system. Based on your theory, you develop one or more hypotheses about the problem. A hypothesis is a testable idea for solving the problem. The nice thing about a hypothesis is that it is either true or false, which works well with our Boolean programmer brains: either/or, black or white, true or false, no ”fifty shades of gray.”

The key here is to write all of this down. When I was young, I never wrote things down because I thought I could keep them all in my head. But that was nonsense; I couldn’t keep them all in my head, and I didn’t know the ones I’d forgotten until my boss at the time asked me a question I couldn’t answer. Few things suck as much as knowing that you’ve got a dumb look on your face in response to a question about something you’re working on.

Eventually I developed a system of note taking that allowed me to make this a bit easier. When I have a theory about a problem, I create a note titled THEORY, and write down my idea. Under this, I write up all my tests (which I call TEST because, like any good programmer, I don’t want to keep typing HYPOTHESIS). The note-taking system I currently use is Org mode in Emacs, which lets you create sequences that can be tied to hot keys, allowing you to change labels quickly. For bugs, I have labels called BUG, ANALYZED, PATCHED, —, and FIXED, while for hypotheses I have either PROVEN or DISPROVEN.

I always keep both the proven and disproven hypotheses. Why do I keep both? Because that way I know what I tried and what worked and what failed. This proves to be invaluable when you have a boss with OCD, or, as they like to be called, ”detail oriented.” By keeping both your successes and failures, you can always go back, say in three months when the code breaks in a disturbingly similar way to the bug you closed, and look at what you tested last time. Maybe one of those hypotheses will prove to be useful, or maybe they’ll just remind you of the dumb things you tried, so you don’t waste time trying them again. Whatever the case, you should store them, backed up, in some version-controlled way. Mine are in my personal source-code repo. You have your own repo, right? Right?!


InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020